why do you need to build further protection when the controllers there are quite capable in providing it using the expensive equipment they have got.
How do you guarantee protection against unknown traffic, which may or not be squawking ?? You don't. You try to provide separation but it can never be guaranteed.
Inverness is building up in to a busy little place, in an area where there are lots of legitimate discrete operations by uncontrolled aircraft. I can understand therefore why they are looking for something to protect the approach airspace.